comparison test 57 vs 50 trim

[mopar2ya]

A DSM 2.0 w/ cast header was the test car, everything was the same except for a turbo swap.

57 trim
15 psi 401 h.p.
20 psi 358 h.p.

50 trim
15 psi 425 h.p.
20 psi 445 h.p.

These are wheel h.p. numbers. This shows the 57 is a high volume low pressure turbo nicely suited for 8V heads. I'll see if I can get the plots to see where the power for each was comming on. Anyway just foor for thought.

[Frank]

I dont understand what you mean by a "high volume, low pressure" turbo. There is no such thing. A turbo flows x cfm or x lb/min of air. The compressor map says what its efficency is when you begin to restrict the air coming out. Nothing more nothing less.

If you really mean that the turbo flows more air at less psi, well no also. Unless you mean turbo flows more air at less psi at the intake, well no again. The car is like apples to oranges to our cars.

From what I can tell, the 50trim makes way more power because of the where this displacement and rpm range place it in the compressor map.... efficency islands. What turbine, btw?

Thats my food for thought... not trying to be an arse or anything, but I dont see it.


Frank

[mopar2ya]

I believe it was a bullseye .63, I need to check to be 100%. Frank, I think we are stating the same thing in different ways. What I mean by high volume low pressre, is that it moves alot of volume in a quick manner then falls off. Much like a sprinter vs a distance runner, the sprinter comes out quick but was built for a short burst.

I would differ on your explaination on air flow."If you really mean that the turbo flows more air at less psi, well no also. Unless you mean turbo flows more air at less psi at the intake, well no again"

Different blade designs and pitches/trim can have the same sized wheel and flow differently. A compressor is simply a fan that moves volume, same as a radiator fan. We all agree that there are different blade designs that are the same size but will move differnt cfm. Again like a aircraft prop, its the same size but if you change the props trim it changes the amount of air it moves.

More testing will be done with the SC61 and several others, all on the same car and same dyno.

[mopar2ya]

Another analogy is a boat prop, same diameter prop but different pitch, one pulls the boat out of the water quickly but has less top end, the other not quite as quick but more top end.....

[Frank]

I took your approach and went a little bit crazy with it.

Well when comparing to the 8v, the same high volume, low pressure wont apply. This is because there is a certain amount of restriction in our cars. The boost is going to climb no matter what unlike higher flow/rpm motors. Of course they can breath the air more freely, so the boost doesnt climb as high. This is for the same reason that I dont think you can squeeze any more out of your 50trim on your car and others who run the turbo have more measured boost on their car with the same hp.

Boost is a measure of restriction, nothing more then that. I am definently interested in the results. I just think that the 57 trim is a horrible choice for our cars.


frank

[Frank]

I understand with the pitch completely... however it is also is what defines the map itself. If you are running the car outside the efficency islands like on the 57trim, the air is hotter and will be less dense and will make less hp.

Just like if you increase the pitch to much, you cavitate on a boat or airplane.


Frank

[mopar2ya]

Boost is a measurement of restriction, but boost isnt just boost, like 20 psi isnt 20 psi. We all know the 20 psi from a mitsu turbo isnt going to make the h.p. 20 psi from a T3T4 would. its simply a matter of compressor efficiency.

cavitate or stall the air, I think thats what happening to a 57 trim at higher boost, why else would the h.p. fall like it did in the test.

[Phreakish]

its all about how much input energy is needed to flow x amount of air - to get that airflow, in certain configurations, you need to raise the pressure (or it'll raise on its own). At that point it becomes a game of design - a compressor that can flow good air AND build boost without turbulating and throwing out hot air that just happens to be at a higher pressure, vs a compressor built to reach higher pressures.

I think I understand both of ya, but its a little hard to follow with the diff anaologies and such for a lot of ppl.

A 'high flow, high pressure' compressor is going to be one that can maintain a good flow quality despite the back-pressure exerted on the output side of the compressor end of the turbo - some compressors will flow MASSIVE air, but cant take the back-pressure before efficiency drops off the map and hot thin air is the only product... Right?

[Frank]

Quote:

Originally Posted by mopar2ya Boost is a measurement of restriction, but boost isnt just boost, like 20 psi isnt 20 psi. We all know the 20 psi from a mitsu turbo isnt going to make the h.p. 20 psi from a T3T4 would. its simply a matter of compressor efficiency.

hence what i said above.... it also has to do with there the shaft rpm falls because of the turbine match up.

Quote:

cavitate or stall the air, I think thats what happening to a 57 trim at higher boost, why else would the h.p. fall like it did in the test.

I think its more of a system effect... shaft speed, efficency island, and rpm range (could also be a timing effect).


Frank

[Frank]

Yeh its all in how we learn about turbos.... I know personally approach it different from others. I start from inside the engine and work my way out when sizing.


Frank

[ACR Turtle]

So based on all the analogies, will my 57 trim T3/T4 make quicker boost but fall off at a lower RPM than a 50 trim with everything else being equal?

[mopar2ya]

It will more more volume quicker, but will become more inefficient at higher pressures quicker than a 50 trim.

[Ondonti]

Quote:

Originally Posted by ACR Turtle So based on all the analogies, will my 57 trim T3/T4 make quicker boost but fall off at a lower RPM than a 50 trim with everything else being equal?

Not really.

Your turbine is gong to decide on most of the spoolup characteristics. The Compressor is goning to determine the density of that air being pushed. with the 57 trim on a good flowing 2+L motor, it just pushes hot air to accomplish the same psi rating as a 50 trim which is still pushing cool air.

[ACR Turtle]

I've read on AGP's website that they seem uninterested in selling a 57 trim turbo to the SRT guys and the TD guys don't seem to care for them, what are they good for, because they also seem to dirty up my papers and my jon boat still floats away.

[Ondonti]

The big difference here is that the 50 trim can hold higher than 70% efficiency ratings where at the same boost leve, the 57 trim is 55%. if the computer is forced to retard ignition because of detonation with the hot air from the 57 trim, you will see a huge power loss.